Configure Rollup to ignore external dependencies

Rollup is now configured to not bundle external dependencies. This allows Material-UI to be used in the project while not inflating bundle sizes or causing duplicated instances of @material-ui/styles from being included in an app.

All of this was to support using the default theme's box shadow for Contained-disabled buttons.

This is a backwards-incompatible change

It is no longer necessary to import createMuiTheme in your app and generate a theme from the exported configuration. Simply import theme from @uw-ui-development/uw-material-ui-react and pass it to the theme provider (<ThemeProvider theme={theme}>...</ThemeProvider>).

Please review: @ahoffmann @JJONES42